Where is telephone country code 859?

There is no telephone country code +859(dialed as 00 859 from many places). It is unused. There are no valid international numbers beginning with +859.

North American area code +1 859 serves Lexington and Covington, Kentucky, USA.

(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)